Fuel pump



Oct. 13, 1936. K. c. BURKHART 2,057,624

FUEL PUMP Filed Sept. 18, 1935 KENNETH 6. .BUEKHHRT INVENTOR MAW";

AT RNEY Patented Oct. 13, 1936 UNITED STATES PATENT OFFICE FUEL rum Kenneth G. Burkhart, Prosser, Wash. Application September 18, 1935, Serial No. 41,043 2 Claims. (01. 103-41) This invention relates in general to fuel pumps used in fuel systems of internal combustion en- .gines and relates specifically to a fuel pump of the type having as a part of,its structure a pres- 5 sure responsive, reciprocatory pumping member and inlet and outlet check valves.

' The invention consists in supplying a vent to allow fuel that is trapped in the pumping chamber of a fuel pump to flow toward the fuel supply.

This vent operates to relieve the pressure existing in the pumping chamber when the pump is stopped during the portion of itscycle that it is discharging fuel. A somewhat uniform'though pulsating pressure is realized from the outlet, in

pumps of current construction, by employing rensilient means which conditionally advance the pumping member during its discharge stroke, and

by interposing an air-dome for a hydraulic cush- 1 ion. When the pump is stopped during the particular party of its cycle in which the linkage has released the diaphragm, spring pressure discharges the reservecapacity of the pump, and in this manner, the fuel pump often continues supplying fuel under pressure for some time there- 5 after. If the float valve in the carburetor has the least tendency to leak, a charge of fuel flows past it and into the float chamber. The resulting rise in fuel level causes the carburetor to overflow or the mixture to be too rich when starting if the motor is warm, making starting difficult and causing uneven idling until the normal level is attained.

The fuel pumps now in general use with internal combustion engines do not provide escaping means for the fuel which is confined in the pumping chamber except the outlet check valve which allows the fuel to flow toward the carburetor. If

the float valve in the carburetor, which opens or closes in response to the fuel level within the carburetor, closes the inlet fuel passage of the carburetor, the fuel cannot escape even into the carburetor. Furthermore, in the ,normal operation of the fuel pump, the spring disposed beneath the diaphragm tends to normally force the diaphragm upward and thereby forces the fuel through the outlet check valve; but, if the carburetor has a sufficient supply of fuel and the float valve prevents the entrance of the fuel being v through the outlet check valve.

--stroke, and is further capable of dampening and These forces tend to viundue wear and frequent replacement of said )valve.

It has also been found that, when the engine ceases to operate, and if at said time, the diaphragm happens to be on the discharge stroke, it 5 necessarily tends to return to its normal position. of rest due to the action of the spring lying thereunder. When the diaphragm is in this position, the pump chamber is charged with fuel, and the inlet valve is closed. Consequently, some of the 10 fuel is displaced by the movement of the diaphragm to its normal position of rest; and the displaced fuel must of necessity pass through the outlet check valve toward the carburetor. If the carburetor float valve is new and tight fitting, it 15 will successfully resist the entrance of this excess fuel into the carburetor; but as soon as there is the slightest wear on the float valve, this displaced fuel will enter into the carburetor and flood the same, making it difiicult to re-start the engine.

It is within the contemplation of my invention to overcome the above inherent disadvantages of the present type of fuel pumps. This is accomplished by providing escaping means between the 25 fuel supply line and the carburetor, but preferably within the fuel pump structure so that the displaced fuel will return to the .supply line rather than attempt to pass into the carburetor The quintessence of the invention is to provide 30 a by-pass or relief port which is capable of preventing the flow of fuel into the carburetor after the internal combustion engine has been stopped with the pumping member on the discharge relieving the shock present in the pulsating and surging of the fuel and, in this manner, the excessive vibration of the float valve of the carburetor is for all practical purposes eliminated. 40

An important object of the invention is to provide a fuel pump which avoids the flooding of the carburetorafter the motor has been stopped.

An equally important object of the invention is to provide means within the fuel pump which 45 prevents the excessive vibration of the float valve in the carburetor.

Not all the advantages and characteristic features have here been stated. Many more will become apparent from the following description and accompanying drawing which illustrates the application of the invention, and in which:

Figure 1 is a side elevation of a fuel pump of the diaphragm type shown connected to a carburetor,

a part of the fuel pump structure being broken 5 away to illustrate the position of the inlet check valve embodying my invention during the intake stroke of the fuel pump. 7

Figure 2 is a side elevation, partially in section, of the fuel pump shown in Figure 1, graphically illustrating the position of the inlet check valve embodying my invention at the beginning of the discharge stroke of the diaphragm.

Figure 3 is a fragmentary, sectional, side elevation of the inlet check valve embodying my invention showing the details of construction of said valve.

Figure 4 is a fragmentary, sectional, side elevation of a portion of a fuel pump, showing the embodiment of my invention in a modified form as a part of the pump casing rather than a part of the inlet check valve. v

Like reference characters are intended to identify similar parts throughout the several views.

The fuel pump, generally designated by reference character A, is of the diaphragm type and is normally attached to the craank case I in any well known manner. There is an opening 2 in the crank case through which rocker arm 3 of the fuel pump passes. Disposed on the cam shaft 4 is an eccentric cam 5 which engages with the surfac 6 of rocker arm 3 to actuate the rocker arm. The fuel pump consists of a body element 'I having therein an irregular interior 8 inwhich there is secured diaphragm 9. Diaphragm 9 is composed of a. specially treated flexible material which is impervious to gasoline and benzol and forms a.

pump chamber In within the interior 8. Disc I'l' is disposed on the top surface of the diaphragm 9 and disc I2 is'disposed adjacent the bottom surface of the diaphragm. These discs are held in tight working relationship to the diaphragm}! by v which rocker arm 3 is journaled. End I9 of in through which shaft l8 passes.

rocke arm 3 has a yoke, not shown, formed there- Link 2| has one of its ends 22 passing through the slot (not shown) formed within stem I 3 and the other end 23 is journaled on shaft l8 so that the'inclined surface of end 23 of link 2| coincides with the inclined surface which is formed at the base of the yoke. A resilient member 24 is held between anchor surface 25 formed within body" element 1 capable of sitting on seat30 formed within the inlet port against the normal thrust of a resilient element, such asa spring 3 I. Disc 29 has a relief port or opening 32 formed therein, the purpose of which will be clarified in the modus operandi to be forthwith set forth. An outlet port 33 also communicates with the pump chamber I and leads to the carburetor 34. An outlet check valve, generally designated by reference character C, is disposed within the port 33 and consists generally of a disc 34 capable of being seated upon seat 35 by the thrust action of a resilient element, such as spring 36.

M odus operandi It at once becomes obvious that the downward movement of the diaphragm is controlled by the linkage which in turn is controlled by the eccentric cam on the cam' shaft. The rotation of the eccentric cam actuates the rocker arm 3 which pushes link 2| downward causing a downward pull to be exerted against stem l3 which pulls the diaphragm 9 downward against the spring l5. Since the diaphragm in its movement almost fills the pump chamber II), it becomes clear that in its downward movement a negative pressure approaching a vacuum is created in the pump chamber.

On the suction stroke of the pump, fuel enters I from the sediment chamber 28 through the inlet check valve B into the pump chamber 10. In this position, the cam shaft is rotated to the low side of the eccentric cam 5. On the return stroke of the pump, the spring pressure thrusts the diaphragm upward forcing fuel from the pump chamber I!) through the outlet check valve C into the carburetor. But when the carburetor bowl is filled, the fioat in the carburetor shuts off the valve, causing the pumped fuel to accumulate and remain in the pump chamber under sufiicient pressure to resist the upward movement of the diaphragm 9 against the thrust of the spring 8.

The braking and regulating action on the normal pulsating flow of the fuel from the pump to the carburetor vibrates excessively the carburetor valve and causes undue wear thereon. Furthermore, if the carburetor valve is not tight fitting due to wear or other conditions, such a braking action is impaired and the fuel continues to fiow into the carburetor and floods the same. Relief port 32, formed in disc 29,allows a part of the fuel which is forced back by the carburetor valve to flow back into the sediment tank 28. By this construction, excessive vibrations caused to the carburetor valve in normal operation are dampened and the flooding is prevented by maintaining the valve in good condition, and by providing a vent to relieve pressure in the pumping chamher after the motor is stopped. The port or opening 32, while sumcient in area to allow a portion of the confined fuel to fiow back into the sediment tank, does not noticeably impair the efficiency of the operation of the inlet check valve or any other part or action of the pump.

The same result may be obtained by providing a relief passage 31 within the pump casing so that it communicates with inlet port 21 and sediment chamber 28,- as. graphically illustrated in Figure 4. I The invention has been described in connection with a specific illustrative embodiment disclosing a definite arrangement of parts. However, it will be understood that many variants thereof are possible to those skilled in-the art, and the invention, in its broader aspect, is not limited to the specific construction herein described and shown, as changes in size, proportions, configurations, substitutions and combinations of forms,

- parts, members and features, may be made without departing from the broad spirit of this invention.

claim as new'and upon which I desire tosecure Letters Patent is: v

1. In a pump of the classdescribed, in combination with a diaphragm, linkage for operating said diaphragm, an inlet check valve and an outlet check valve, of a valve disc incorporated within the inlet check valve, said valve disc having embodied therein a relief port adapted to receive excessive fuel from the pump chamber and to dampen the excessive pulsations of the carburetor valve and diaphragm.

2. In combination with a pump of that type which includes a pressure-responsive reciprocatory pumping element movable in one direction in v a pumping chamber by actuating means serving to impart variable strokes, and conditionally advanced in the opposite direction by resilient means during its discharge strokes, of an inlet check valve comprising a valve disc, said valve disc having a port therein adapted to by-pass a' flow of excess fuel displaced from the pumping chamber by action of said resilient means after said actuating means have ceased to function during the discharge stroke.

KENNETH C. BURKHAR'I'. 

